US6404200B1 - Magnetic resonance tomography apparatus with vacuum-insulated gradient coil system - Google Patents

Magnetic resonance tomography apparatus with vacuum-insulated gradient coil system Download PDF

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Publication number
US6404200B1
US6404200B1 US09/649,497 US64949700A US6404200B1 US 6404200 B1 US6404200 B1 US 6404200B1 US 64949700 A US64949700 A US 64949700A US 6404200 B1 US6404200 B1 US 6404200B1
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Prior art keywords
gradient coil
magnetic resonance
field magnet
coil system
tomography apparatus
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Expired - Fee Related
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US09/649,497
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English (en)
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Peter Dietz
Matthias Gebhardt
Wolfgang Renz
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Siemens AG
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Siemens AG
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Assigned to SIEMENS AKTIENGESELLSCHAFT reassignment SIEMENS AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GEBHARDT, MATTHIAS, DIETZ, PETER, RENZ, WOLFGANG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
    • G01R33/385—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils
    • G01R33/3854—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils means for active and/or passive vibration damping or acoustical noise suppression in gradient magnet coil systems

Definitions

  • the present invention is directed to a magnetic resonance tomography apparatus that contains a basic field magnet system and a gradient coil system.
  • Magnetic resonance tomography is a known technology for acquiring images of the inside the objects of, in particular, the body of a living examination subject.
  • a magnetic resonance tomography apparatus has a space for the acceptance of the examination subject, what is referred to as an examination space or volume.
  • the examination space is at least partially spatially limited by a surface of the apparatus that surrounds it.
  • the majority of the aforementioned limiting surface is normally formed by a surface belonging to the gradient coil system and another, normally a small portion is formed by a part of an outer envelope of the basic field magnet system.
  • the basic field magnet system At least in a partial volume sub-region of the examination space, the basic field magnet system generates an optimally uniform, static basic magnetic field on which the gradient coil system superimposes rapidly switched magnetic fields with approximately constant gradients, referred to as gradient fields, in all three spatial directions.
  • Currents whose amplitudes reach several 100 A and that are subject to frequent and fast changes in the current direction with rise and decay rates of several 100 kA/s thereby flow in the gradient coils. These currents are controlled on the basis of pulse sequences and, in the presence basic magnetic field on the order of magnitude of one Tesla, cause oscillations (vibrations) of the gradient coil system due to Lorentz forces.
  • the entire surface of a magnetic resonance tomography apparatus essentially includes the outer envelope of the basic field magnet system—which forms by far the greatest part—as well as the surface of the gradient coil system, including the devices such as radio frequency antennas mounted at the gradient coil system.
  • the envelope of the basic field magnet system is the dominant noise source. This is also true for the examination space, which is essentially limited by the surface of the gradient coil system.
  • a first transmission path proceeds via a more or less thin intermediate layer between those surfaces of the gradient coil system and the basic field magnet system that directly adjoin one another. This intermediate layer is normally filled by air, which behaves as a transmission medium air.
  • a second transmission path proceeds via a direct mechanical connection of the gradient coil system to the basic field magnetic system, for example due to a press fit of the gradient coil system in a hollow opening of the basic field magnet system.
  • German OS 38 33 591 discloses a magnetic resonance tomography apparatus with a tubular gradient coil system which is arranged without supports inside the hollow opening of the basic field magnet system, and which is adjustably carried by a supporting frame that is located outside the basic field magnet system. To this end, the entire gradient coil system is lengthened beyond the longitudinal dimension of the basic field magnet system. The intent is for no mechanical oscillations of the gradient coil system to be transmitted onto the basic field magnet system, and to allow the gradient coil system to be correctly adjustable in the basic magnetic field.
  • the direct mechanical transmission of oscillations via the aforementioned second transmission path is in fact suppressed; however, the aforementioned first transmission path via the intermediate layer is neither damped nor suppressed.
  • German OS 195 31 216 discloses a magnetic resonance tomography apparatus with a gradient coil system secured to the basic field magnet system via at least one support mount, wherein the support mount is located in the region of an oscillation node of the gradient coil system that is expected during operation.
  • the support mount includes a damping element. Disadvantageous influences of oscillations of the gradient coil system, for instance acoustic and structural noises, as well as in the image quality (artifacts) are to be avoided as a result. Although improvements again are achieved for the second transmission path, the first transmission path is again neither damped nor suppressed.
  • German OS 197 34 138 discloses a magnetic resonance tomography apparatus with a gradient coil system arranged in a vacuum encapsulation for reducing noise.
  • the gradient coil system is carried within the vacuum encapsulation by a number of insulating or individually damping fastening devices that are arranged spaced from each other.
  • the fastening devices are formed either as a rubber-like damping fastening with rigid support mount or as a spring-damping fastening with a supporting flange.
  • the fastenings are connected to the gradient coil system and the rigid support mount or the supporting flange of each fastener is connected to the vacuum encapsulation.
  • a damping of the second transmission path and a suppression of the first transmission path dependent on the quality of the vacuum are thereby achieved.
  • German OS 44 32 747 discloses a fundamental reduction of oscillations of the gradient coil system on the basis of an active measure.
  • a force generator particularly containing piezoelectric components, is arranged in or at the gradient coil system. These components generate forces that oppose the oscillations of the gradient coil system, so that a deformation of the gradient coil system is essentially prevented.
  • the piezoelectric components are suitably driven by a voltage applied to them.
  • the introduction or attachment of a number of piezoelectric components into the comparatively spatially extensive gradient coil system, the voltage supply lines thereto, as well as the drive circuitry involve great technical and economic outlay.
  • An object of the present invention is to provide an economical magnetic resonance tomography apparatus with low noise emission that avoids the aforementioned disadvantages.
  • a magnetic resonance tomography apparatus wherein at least a part of a vacuum housing of an evacuatable space is formed by at least one portion (surface region) of the basic field magnet system, preferably a region of the outer envelope thereof, and by at least one portion (surface region) of the gradient coil system.
  • Components thus are utilized for the formation of the evacuatable space for the purpose of noise reduction that are already necessary for the operation of a magnetic resonance tomography apparatus and that often already have the property of vacuum tightness.
  • a closed, separate, expensive vacuum housing is not necessary because regions of the gradient coil system as well as of the basic field magnet form a majority of the vacuum housing.
  • the evacuatable space extends at least between those surfaces of the basic field magnetic system and of the gradient coil system facing directly toward one another.
  • at least the intermediate layer of the initially cited, first transmission path can be contained in a vacuum. The first transmission path for noise-producing oscillations thus can be suppressed.
  • the aforementioned vacuum housing is formed by the vacuum housing of a basic field magnet system having superconducting coil arrangement.
  • a part of the vacuum housing of the superconducting basic field magnet system that is needed anyway is substituted by the gradient coil system. This saves material and thus costs. Moreover, more freedom is gained within the volume in the examination space.
  • a further part of the vacuum housing of the evacuatable space is formed by a seal flange.
  • a closed vacuum housing for the evacuatable space between gradient coil system and basic field magnet system already can be realized with the utilization of seal flanges in many apparatuses. This represents a very simple and economical solution. Further, only minimal structural adaptations are necessary given conventional magnetic resonance tomography apparatus to produce the evacuatable space between those surfaces of the basic field magnet system and of the gradient coil system facing directly toward one another. Further, the accessibility of the surface of the gradient coil system facing away from the basic magnet system, and the case for maintenance and repair, are not impaired. The aforementioned surface of the gradient coil system—to which radio frequency antennas are often secured—remains freely accessible.
  • the vacuum housing of the evacuatable space contains a valve device that enables an evacuation of the evacuatable space.
  • the implementation of a seal flange with the aforementioned valve device is especially advantageous.
  • the valve device creates the possibility of evacuating the evacuatable space, for example by pumping out with a vacuum pump, after the mounting of the seal flange has ensued.
  • a seal flange can be removed and re-mounted after the end of the work and the vacuum can be restored in a simple way.
  • the gradient coil system is connected in a weight-bearing fashion to the basic field magnet system at the location of the dominant natural oscillation node of the gradient coil system.
  • the noise propagation via the second transmission path is thereby also reduced.
  • German OS 195 31 216 is referenced for a detailed description of the fastening of the gradient coil system at its dominant natural oscillation node.
  • the magnetic resonance tomography apparatus has a carrier for the gradient coil system that enables support of the gradient coil system, preferably at the floor of an installation room, in a manner that is decoupled from the basic field magnet system.
  • a hollow-cylindrical (tubular) gradient coil system has carrying elements projecting from the lower region of an end face perpendicular to the principal cylinder axis.
  • a support that is decoupled from the basic field magnet system is possible by lengthening the gradient coil system in that region wherein a transport and support device for an examination subject, for example a patient bed, is normally arranged. Differing from an extension of the complete gradient coil system, the accessibility to the examination space is hardly restricted and the confining volume is not enlarged which is important for acceptance by patients having claustrophobia.
  • the support of the gradient coil system decoupled from the basic field magnet system nearly completely suppresses the second transmission path.
  • the basic field magnet system preferably the outer envelope thereof, and/or a connection between the gradient coil system and the basic field magnet system, contains at least one part of a decoupling mechanism that prevents the propagation of oscillations of the gradient coil system onto the overall outer envelope of the basic field magnet system.
  • the decoupling mechanism contains a device, preferably embodied as a bellows or an element made of elastic material, that acts in oscillation-decoupling fashion due to its mechanical properties.
  • the decoupling mechanism contains actuators, preferably embodied as piezoelements, whose spatial size is designed such that they have an oscillation-decoupling effect.
  • the aforementioned German OS 44 32 747 is referenced for a detailed disclosure of the fundamental functioning of piezoelements for oscillation suppression.
  • piezoelements are not arranged over the comparatively spatially extensive gradient coil system; rather, in accordance with the invention piezoelements are arranged in a comparatively small spatial region, for example in the proximity of the connection between the gradient coil system and the basic field magnet system. In this small region, they prevent a transmission of oscillations of the gradient coil system onto the envelope of the basic field magnet system.
  • the economic outlay for this is correspondingly more beneficial and a significant noise-reducing effect is still achieved.
  • FIG. 1 is a longitudinal section through an inventive magnetic resonance tomography apparatus having sealing flanges and having a gradient coil system secured at its natural oscillation node.
  • FIG. 2 is a longitudinal section through an inventive magnetic resonance tomography apparatus having seal flanges and having a gradient coil system that is mounted independently of the basic field magnet system.
  • FIG. 3 is a longitudinal section through an inventive magnetic resonance tomography apparatus having a gradient coil system as part of the vacuum housing of a superconducting basic field magnet and having a decoupling mechanism.
  • FIG. 4 is a schematic, detailed illustration of the decoupling mechanism from FIG. 3 in an embodiment with a bellows.
  • FIG. 5 is a schematic detailed illustration of the decoupling mechanism of FIG. 3 in an embodiment with actuators.
  • FIG. 1 shows a longitudinal section through a hollow-cylindrical basic field magnet system 1 having a hollow opening wherein a hollow-cylindrical gradient coil system 2 is arranged.
  • the gradient coil system 2 is connected to the basic field magnet system 1 via connecting devices 3 at the dominant natural oscillation node which is expected during operation.
  • the connecting devices 3 thereby produce a connection between the gradient coil system 2 and the basic field magnet system 1 at a number of points along the circumference. Due to the attachment of two seal flanges 4 , an interconnected, evacuatable space 5 arises between those surfaces of the gradient coil system 2 and of the basic field magnet system 1 facing directly toward one another.
  • One of the seal flanges 4 contains a valve device 6 that enables an evacuation of the evacuatable space 5 , for example in conjunction with a vacuum pump connected thereto.
  • the seal flanges 4 are connected to the gradient coil system 2 and to the basic field system 1 in easily releasable fashion, for example via screwed connections.
  • the seal flanges 4 can be removed, for example for the purpose of maintenance or repair tasks at the overall gradient coil system 2 , and can be remounted after the end of the work.
  • the valve device 6 thereby allows an evacuation of the evacuatable space 5 after the end of the aforementioned tasks.
  • valve device 6 can be fashioned such that the evacuatable space 5 is aerated via the valve device 6 before beginning the work. Due to the vacuum in the evacuatable space 5 , transmission of oscillations of the gradient coil system 2 via the intermediate layer between the two systems in the sense of the initially cited, first transmission path is prevented during operation of the apparatus. Further, the connection of the gradient system to the basic field magnet system 1 at its dominant natural oscillation node also at least damps the transmission of oscillations via the direct mechanical connection in the sense of the initially cited, second transmission path. Care should be exercised in the implementation of the seal flange 4 and/or the fastening thereof so that a noise-producing transmission of oscillations in the sense of the second transmission path does not again occur via this component.
  • FIG. 2 shows a longitudinal section through a magnetic resonance tomography apparatus having the hollow-cylindrical basic field magnet system 1 and the gradient coil system 2 .
  • the gradient coil system 2 in FIG. 2 is not connected to the basic field magnet system 1 at its dominant natural oscillation node.
  • the hollow-cylindrical gradient coil system 2 has carrying elements 7 projecting perpendicularly to the principal cylinder axis in the lower region at both end faces.
  • the carrying elements 7 enable a support of the gradient coil system 2 decoupled from the basic field magnet system 1 via a carrying device 8 , for example on a floor 9 of an installation room.
  • a carrying device 8 for example on a floor 9 of an installation room.
  • FIG. 3 shows a longitudinal section through a magnetic resonance tomography apparatus having the hollow-cylindrical basic field magnet system 1 .
  • the basic field magnet system contains a superconducting coil arrangement 10 .
  • the superconducting coil arrangement 10 is surrounded by at least one cold shield 11 , and the cold shield 11 is in turn surrounded by a vacuum housing 12 .
  • the gradient coil system 2 is connected via a decoupling device 13 to the remaining vacuum housing 12 , whereby the gradient coil system 2 and the decoupling mechanism 13 being components of the vacuum housing 12 .
  • the decoupling mechanism 13 is thereby two-piece, with each part being annularly fashioned.
  • the decoupling mechanism 13 functions as a support connection for the gradient coil system 2 with respect to the remainder of the vacuum housing 12 and prevents the propagation of oscillations of the gradient coil system onto the remainder of the vacuum housing 12 in the sense of the second transmission path.
  • the propagation of oscillations in the circumferential direction of the hollow-cylindrical gradient coil system 2 that are especially relevant in noise production, is suppressed.
  • the vacuum within the vacuum housing 12 prevents the transmission of oscillations in the sense of the first transmission path.
  • the embodiment according to FIG. 3 is especially economical.
  • the decoupling mechanism 13 is releasably connected to the gradient coil system and/or to the remaining vacuum housing 12 , and a component of the vacuum housing 12 has a valve mechanism 6 available to it.
  • FIG. 4 shows a cross-section through one of the annular versions of the decoupling mechanism 13 from FIG. 3 .
  • a decoupling mechanism 13 a is thereby shown that has two stiffening elements 14 and a bellows 15 .
  • One of the stiffening elements 14 is, for example, connected rigidly and vacuum-tight to the remainder of the vacuum housing 12 and the other is connected to the gradient coil system 2 .
  • the bellows 15 is designed for damping oscillations in circumferential directions of the hollow-cylindrical gradient coil system 2 . These oscillations are especially relevant in the production of noise.
  • the decoupling mechanism 13 a In the direction of the principal cylinder axis, the decoupling mechanism 13 a , particularly the bellows 15 , represents a rigid connection. This prevents an oscillation of the overall gradient coil system 2 in the direction of the principal cylinder axis of the hollow-cylindrical gradient coil system 2 from leading to distortions (artifacts) in magnetic resonance images.
  • FIG. 5 shows a cross-section through another of the annular versions of the decoupling mechanism 13 from FIG. 3 .
  • a decoupling mechanism 13 b is thereby shown that contains a number of piezo-elements 16 and stiffening elements 14 .
  • the piezo-elements 16 expand or contract according to the indicated arrow directions.
  • An oscillation-damping or oscillation-decoupling effect thus can be controlled, similar to the bellows from FIG. 4 .
  • the decoupling mechanism 13 b is fashioned similar to the decoupling mechanism 13 a of FIG. 4 .

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
US09/649,497 1999-08-26 2000-08-28 Magnetic resonance tomography apparatus with vacuum-insulated gradient coil system Expired - Fee Related US6404200B1 (en)

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DE19940550A DE19940550C1 (de) 1999-08-26 1999-08-26 Magnetresonanztomographiegerät mit vakuumisoliertem Gradientenspulensystem
DE19940550 1999-08-26

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6552543B1 (en) * 1999-08-26 2003-04-22 Siemens Aktiengesellschaft Magnetic resonance tomography apparatus with vibration-decoupled outer envelope
US6707302B2 (en) * 2001-06-07 2004-03-16 Siemens Aktiengesellschaft Magnetic resonance apparatus having a basic field magnet with damping of mechanical oscillations
US20040061499A1 (en) * 2002-09-30 2004-04-01 Siemens Aktiengesellschaft Magnetic resonance device
US6774631B2 (en) * 2000-04-25 2004-08-10 Siemens Aktiengesellschaft Magnetic resonance gradient coil with a heat insulator disposed between the electrical conductor and the carrier structure
US20040158164A1 (en) * 2002-03-14 2004-08-12 Patricia Arand Method and system for detection of left ventricular hypertrophy
US20050156595A1 (en) * 2002-05-08 2005-07-21 Cornellis Leonardus Gerardus Ham Magnetic resonance imaging apparatus with reduced noise production
US20050285596A1 (en) * 2004-06-23 2005-12-29 Kunihito Suzuki Magnetic resonance imaging apparatus
US20060103384A1 (en) * 2004-11-18 2006-05-18 Mitsubishi Denki Kabushiki Kaisha, Magnetic apparatus, installation method for magnetic apparatus, and magnetic resonance imaging diagnosis system
US20070164743A1 (en) * 2006-01-19 2007-07-19 Kabushiki Kaisha Toshiba Magnetic resonance imaging apparatus
US20070176602A1 (en) * 2004-03-15 2007-08-02 Koninklijke Philips Electronics N.V. Main magnet perforated eddy current shield for a magnetic resonance imaging device
US20070182516A1 (en) * 2004-03-16 2007-08-09 Koninklijke Philips Electronics N.V. Magnetic resonance imaging device with an active shielding device
GB2458950A (en) * 2008-04-04 2009-10-07 Siemens Magnet Technology Ltd Vacuum Chamber Construction for MRI Apparatus
CN102711604A (zh) * 2011-01-13 2012-10-03 株式会社东芝 磁共振成像装置
US20130037297A1 (en) * 2011-02-10 2013-02-14 Andreas Krug Supply line apparatus
US10120046B2 (en) 2015-01-28 2018-11-06 Toshiba Medical Systems Corporation Magnetic resonance imaging apparatus

Families Citing this family (2)

* Cited by examiner, † Cited by third party
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DE10147745C2 (de) * 2001-09-27 2003-07-24 Siemens Ag Kernspin-Tomographiegerät mit Lärmunterdrückung durch Dämpfung von mechanischen Schwingungen
JP4988385B2 (ja) * 2007-03-07 2012-08-01 株式会社日立メディコ 磁気共鳴イメージング装置

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Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6552543B1 (en) * 1999-08-26 2003-04-22 Siemens Aktiengesellschaft Magnetic resonance tomography apparatus with vibration-decoupled outer envelope
US6774631B2 (en) * 2000-04-25 2004-08-10 Siemens Aktiengesellschaft Magnetic resonance gradient coil with a heat insulator disposed between the electrical conductor and the carrier structure
US6707302B2 (en) * 2001-06-07 2004-03-16 Siemens Aktiengesellschaft Magnetic resonance apparatus having a basic field magnet with damping of mechanical oscillations
US20040158164A1 (en) * 2002-03-14 2004-08-12 Patricia Arand Method and system for detection of left ventricular hypertrophy
US20050156595A1 (en) * 2002-05-08 2005-07-21 Cornellis Leonardus Gerardus Ham Magnetic resonance imaging apparatus with reduced noise production
US7400146B2 (en) * 2002-05-08 2008-07-15 Koninklijke Philips Electronics N.V. Magnetic resonance imaging apparatus with reduced noise production
US20040061499A1 (en) * 2002-09-30 2004-04-01 Siemens Aktiengesellschaft Magnetic resonance device
US20070176602A1 (en) * 2004-03-15 2007-08-02 Koninklijke Philips Electronics N.V. Main magnet perforated eddy current shield for a magnetic resonance imaging device
US7372271B2 (en) 2004-03-15 2008-05-13 Koninklijke Philips Electronics N. V. Main magnet perforated eddy current shield for a magnetic resonance imaging device
US20070182516A1 (en) * 2004-03-16 2007-08-09 Koninklijke Philips Electronics N.V. Magnetic resonance imaging device with an active shielding device
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US20050285596A1 (en) * 2004-06-23 2005-12-29 Kunihito Suzuki Magnetic resonance imaging apparatus
US7205767B2 (en) * 2004-11-18 2007-04-17 Mitsubishi Denki Kabushiki Kaisha Magnetic apparatus, installation method for magnetic apparatus, and magnetic resonance imaging diagnosis system
US20060103384A1 (en) * 2004-11-18 2006-05-18 Mitsubishi Denki Kabushiki Kaisha, Magnetic apparatus, installation method for magnetic apparatus, and magnetic resonance imaging diagnosis system
CN100586369C (zh) * 2006-01-19 2010-02-03 株式会社东芝 磁共振成像装置
US7567082B2 (en) * 2006-01-19 2009-07-28 Kabushiki Kaisha Toshiba Magnetic resonance imaging apparatus
US20070164743A1 (en) * 2006-01-19 2007-07-19 Kabushiki Kaisha Toshiba Magnetic resonance imaging apparatus
GB2458950A (en) * 2008-04-04 2009-10-07 Siemens Magnet Technology Ltd Vacuum Chamber Construction for MRI Apparatus
GB2458950B (en) * 2008-04-04 2010-09-29 Siemens Magnet Technology Ltd Chamber apparatus and method of manufacture thereof
CN102711604A (zh) * 2011-01-13 2012-10-03 株式会社东芝 磁共振成像装置
US20130314089A1 (en) * 2011-01-13 2013-11-28 Toshiba Medical Systems Corporation Magnetic resonance imaging apparatus
CN102711604B (zh) * 2011-01-13 2015-06-10 株式会社东芝 磁共振成像装置
US9939499B2 (en) * 2011-01-13 2018-04-10 Toshiba Medical Systems Corporation Magnetic resonance imaging apparatus
US20130037297A1 (en) * 2011-02-10 2013-02-14 Andreas Krug Supply line apparatus
US8952696B2 (en) * 2011-02-10 2015-02-10 Siemens Aktiengesellschaft Supply line apparatus
US10120046B2 (en) 2015-01-28 2018-11-06 Toshiba Medical Systems Corporation Magnetic resonance imaging apparatus

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JP2001104285A (ja) 2001-04-17

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